Method of decolorizing neutralized fatty oils



July 10, 1956 |.A.AF1EUUS 2,754 10 METHOD OF DECOLORIZING NEUTRALIZED FATTY OILS Filed March 8, 1951 /N VE N TOR. var Axel A feel/us BY mm 2,754,3ill Patented July 10, 1956 METHOD OF DECOLORIZIN G NEUTRALIZED FATTY OILS Ivar A. Afzelius, Bromma, Sweden,

bolaget Separator, of Sweden assignor to Aktie- Stockholm, Sweden, a corporation This invention relates to a method of removing coloring, odorizing and flavoring matters from fatty oils, preferably in conjunction with the neutralizing of free fatty acids.

When a fatty oil containing free fatty acids is treated with a neutralizing agent, coloring, odorizing and flavoring matters are precipitated during the neutralization. They are not separated out completely, however. Oils intended to be used in the manufacture of food stuffs or high quality soap must therefore be bleached and deodorized. But even after such treatment, some oils (for example, rape-seed oil) contain substances which give a characteristic odor and flavor to the oil. These changes become more marked when the oil is stored over long periods. It has been proposed to neutralize and decolorize oils of this kind in two stages by means of lye. In the first stage, the free fatty acids are neutralized. After removal of the soap thus formed, strong lye is added which precipitates coloring, odorizing and flavoring matters. A satisfactory decolorization necessitates a long period of contact between oil and lye. Considerable quantities of neutral fat are thereby saponified which makes the method uneconomical.

The present invention is characterized principally in that an aqueous solution containing a salt of a strong base and a Weak acid, such as soda or secondary sodium phosphate, is mixed with a neutralized oil. The solution may also contain a strong neutralizing agent.

The term decolorizing will be used herein to describe the result of an operation according to the invention. In order to avoid any misunderstanding it should be noted, however, that it also comprises improvements of flavor and odor. The improvement in flavor and odor is often more marked than the improvement of the color but cannot, as in the case of the color, be expressed in figures.

I have found that the following factors affect the result:

(1) pH value of the aqueous solution.

(2) The quantity of alkaline reaction matters dissolved in the aqueous solution.

(3) The quantity of aqueous solution mixed with the oil.

(4) The time of contact between the oil and the aqueous solution.

(5) The temperature at which the decolorization takes place.

If the aqueous solution used for the decolorization is diluted 100 times, the diluted solution should have a pH value higher than 11.0, although solutions having a pH value higher than 12.8 obtained in this manner should not be used as they will cause too heavy oil losses by saponification.

When the decolorization is carried out with soda, a solution should be used, that is, 20 parts by weight of soda dissolved in 80 parts by weight of water. The

decolorization is accelerated and becomes more complete when the aqueous solution is mixed with an alkali lye.

The quantity of lye should be so chosen that the oil will have satisfactory color and odor; if a further quantity of lye is used, the saponification losses may increase considerably.

The quantity of the aqueous solution must be determined according to the qualities of the oil, so that the desired decolorization is attained with minimum losses of oil.

The time of contact depends on the pH value of the aqueous solution, that is, an aqueous solution having a high pH value requires a shorter time of contact than one having a low pH value. We have found that the best result is obtained when the aqueous solution has such properties that the desired decolorization is attained after a time of contact ranging from 10 to 30 minutes.

The temperature during the final stage of the process must be sutficiently high to cause any emulsion formed to be broken. For this purpose, temperatures ranging between 50 and C. are required. When the neutralization and decolorization are eflected according to a continuous method in two successive operations, the aqueous solution is preferably mixed with the unheated oil after the soap has been separated. Some oils may be decolorized with smaller oil losses if the oil is cooled before it is mixed with the aqueous solution. The temperature is then elevated either gradually or rapidly immediately before the precipitated coloring matter is to be separated.

The advantages of the method according to the invention are specially conspicuous in continuous refining when the lye is quickly mixed with the oil and when the soap thereby formed is separated immediately. The time of contact between oil and lye should not exceed 2 minutes. With a short time of contact between oil and lye, the losses by saponification will be small but the decolorization of oils difiicult to refine will be less satisfactory. If lye is then mixed with the oil, considerable quantities of neutral fat will be saponified, since the final decolorization of an oil difficult to refine requires a long time of contact between oil and lye. In this way the advantages of the short time of contact in the first stage are considerably reduced.

It will be understood that the scope of the invention is not limited to neutralization and decolorization in a continuous process but one or both operations may be carried out in batches.

In the accompanying drawing, the single illustration shows schematically a continuously operating plant for neutralization and decolorization in separate stages, according to the invention.

Referring to the drawing, it is assumed that crude oil is led in a continuous stream by the pump 1, through the heater 2 into the centrifugal separator 3. The dosing device 4 supplies lye which is mixed with the oil in the mixer 5, before the oil enters the separator 3. In the latter, the soap is separated from the oil and discharged continuously into pipe 3a. The oil from the separator 3 is fed by the pump 6 into the mixer 7, and the aqueous solution is also fed into mixer 7 by the dosage pump 8. The mixture of oil and aqueous solution is then led in a continuous stream through the reaction vessel 9, which may be provided with an agitator (not shown). The oil is then purified in the centrifugal separator 10.

The results tabulated below were obtained in the processing of rape-seed oil according to the invention. The bottom row of the table indicates decolorization and saponification losses when the oil is decolorized with pure lye. The alkaline solution was made up of a 20% 3 NazCOa solution, and a 14% NaOH solution and mixtures of these in the proportions stated below.

Quantity of alkaline solution: 2.5% of weight of oil. Reaction time; 30 minutes. 7

Temperature: 70 C."

Neutralized oil treated Strength of color in pH-of w1th. Lovibond-units l alkaline Saponifisolution cation diluted losses, NazQOs N aOH 100 times percent solut on, solution, yellow red blue percent percent 0 70 9 9 l 100 0 70 8 8 11. 4 0. 05 75 25 70 7 7 l2. 4 0. 3 50 50 70 6 7 12.7 0 5 25 75 70 6 6 l2. 8 1 3 0' 100 70 6 6 13.0 i 9 1 Cell: 133 mm.

assuming the molecular weight of the fatty acids to be 310. The saponification loss was calculated as the difference between the quantity of fatty acid of the crude oil and the quantity of fatty acid found in the soapstock.

In order to improve the quality and the color, 6% of a solution consisting of 50% soda lye of B. and 50% of a 20% soda solution were added to 200 grams .of the neutralized oil after heating to 80 C. After a contact time of 15 minutes with continuous stirring, the sample was centrifuged at 80 C., whereupon the soapstock was further worked and the saponification loss was determined as described above.

In another test, a treatment with excess alkali was effected without previous separationof the soap. An equivalent quantity of soda lye of 20 B. and also 3% soda lye of 20 Be. and 3% of a 20% soda solution were added to 200 grams of oil at 80 C. After 15 minutes of contact time, the soap was separated and the saponification losses were calculated as described above. The

When decoloring cotton-seed oil in the same way as 20 following Table I summarizes the results obtained.

' Table I .-Alkaline treatment of rape-seed oil Working condi- Quantity of alkali Quantity of Color, Loviboud, 13.3 cm.

ditions added per 200 g. oil fatty acid in Saponificacell, yellow-red-blue Percent soaption loss FFA of oil stock calculated as Temp. Time, ml. soda ml. 20% calculated as percent of Oil treated Bleached oil C. ruins. lye of soda percent of initial oil with alkali (1% bleach- 20" Be. solution initial oil ing earth) 8O 2 9.50 6.03 0.17 70x11x9 35x4x0 80 15 6.00 6.00 1.48 1.40 70x 5X2 35x1.5x0

Total 1. 57

6.86 80 15 15. 50 6. 00 9. 18 3. 32 70 x 7 x 4 35 x 2.5 x 0 described for rape-seed oil, the following results were obtained:

N eutralized oil treated Strength of color in pH of with Lovibond-units 1 alkaline Saponifisolution cation diluted losses, NazQO: NaOH 100 times percent solution, solution, yellow red blue percent percent 0 0 70 38 10 100 0 7O 37 10 11. t 0. 07 75 70 15 4 12.4 0.5 50 50 70 13 3 12. 7 1. 1 as 75 70 1a 3 12.8 1. 7 0' 100 70 11 2 l3. 0 2. 3

1 Cell: 133 mm.

In the preceding, it was assumed that the aqueous solutiouwas mixed with. the oil in one stage. It will beunderstood that the invention also comprises introducing the aqueous solution in batches intotheoil in two or more stages, using a reaction vessel between the stages. The aqueous solution added in one stage maythereby be removed by centrifuging before a further quantity-of aqueous solution is added in the .next stage.

The following specific. examples. show the efiect of thatembodiment of the method in which thesoap formed during the neutralization of the oil is separated before theoilis further treatedwith an alkaline water solution.

EXAMPLE I To 200grams of a rape-seed oil having 5.86%-FFA, 20?.B. soda lye was added at SO C., While stirring. The amount of lye used was. 5% in excess of that necessary to neutralize the quantity of free fatty acid. contained in the. oil, After 2 minutes of stirring, the. mixture. was centrifuged in a test tube centrifuge at 80 C. for 10 minutes, whereupon the soapstock was separated from It will be seen from thetable that the saponification losses were twice as large when the treatment was efifected with excess alkali without separation of the soap, as those incurred when separating the soap with a subsequent treatment of the neutralized soap-free oil with the identical excess of alkali. Furthermore, a better color is obtained both prior to and after the bleaching when applying the latter method.

EXAMPLE II In a continuous operation refinery plant having a capacity of 2 tons of oil per hour and comprising a crude oil pump, an oil pre-heater, a lye dosing pump, a neutralization mixer, a holder tank and an hermetic centrifugal separator, a rape-seed oil containing 4.9% fatty acids was refined. After the oil. had been heated to C., of the quantity of lye necessary for neutralizing the fatty acids was added by means of the pump. The mixture was then passed to the holder tank in which the temperature was kept at 85 C. by a heating jacket, and in which the mixture was held for 15 minutes and finally fed into the hermetic separator, in which the soapstockwas separated from the oil. The soapstock was collected separately and split with sulphuric acid, whereupon the acid-containing water-was drawn oif andthe acid oil was weighed. From 10,875 kgs. of crude. oil, 950 kgs. of split soapstock. and.9.,843. kgs.. of refined oil were obtairied. The refining factor calculated from the obtained quantity of'split'soapstock was thus 1,78, and that calculated from the difference by weight between crude oil and refined oil was 1.94.

In anothertest, the identical rape-seed oil was refined with a 5% excess of lyeof 20 B., theoilbeing fed into the hermetic. separator immediately after having been mixed: with lye,' that is, without allowing a holding time prior tothe separation. After the. soap had been sep: arated in the hermetic separator, 6% of a mixture consisting of 50% lye of 20 B. and 50% of a 20% soda was added whereuponthe mixture was passed into a tank heating jacket -and,- after treatment with alkali, the mix-- ture was separated in an open type centrifugal separator.

The soapstock from the neutralization and alkaline treatment was fed into a common tank in which the soap was split with sulphuric acid. With this method, 735 kgs. of split soapstock and 9,185 kgs. of refined oil were obtained from 9,988 kgs. of crude oil. The refining factor calculated from the quantity of split soapstock was 1.50 and that calculated from the difierence between the quantities of crude oil and neutralized oil was 1.64. Thus, the refining factor was considerably lower than in the previous test in which the alkaline treatment was carried out without previous separation of the soap.

I claim:

1. In the decolorizing of fatty oils after neutralization thereof, the improvement which comprises separating from the oil the soap formed during the neutralization step, and then mixing with the oil an aqueous solution containing a strong base and also a salt of a strong base and a weak acid, said aqueous solution having a pH value higher than 11.0 but no higher than 12.8 after dilution 100 times.

2. The improvement according to claim 1, in which the aqueous solution is maintained in admixture with the oil for a period of to 30 minutes.

3. The improvement according to claim 1, in which the oil is neutralized and decolorized in two continuous successive operations, the neutralizing being eflected with a strong neutralizing agent mixed with the oil, the resulting soap being centrifugally separated from the oil before said agent has been mixed with the oil for two minutes, said separation being followed by said mixing of the aqueous solution with the oil.

4. The improvement according to claim 1, in which said solution is mixed with the oil in batches.

5. In the decolorization of fatty oils after the neutralization thereof, the improvement which comprises separating from the oils the soap formed during the neutralization, mixing the separated oils with an aqueous solution, said solution having a pH value of 11.0 to 12.8 after dilution one hundred times and being in an amount required to give the desired decolorization, the solution having NazCOa in the amount of twenty parts by weight to eighty parts of water, heating the mixture to a temperature of from to C., and after the elapse of a period of from 10 to 30 minutes separating the oil from the aqueous solution.

References Cited in the file of this patent UNITED STATES PATENTS 1,692,226 Schwarcman Nov. 20, 1928 2,242,188 Thurman May 13, 1941 2,607,788 Clayton Aug. 19, 1952 2,641,603 Clayton June 9, 1953 

1. IN THE DECOLORIZING OF FATTY OILS AFTER NEUTRALIZATION THEREOF, THE IMPROVEMENT WHICH COMPRISES SEPARATING FROM THE OIL THE SOAP FORMED DURING THE NEUTRALIZATION STEP, AND THEN MIXING WITH THE OIL AN AQUEOUS SOLUTION CONTAINING A STRONG BASE AND ALSO A SALT OF A STRONG BASE AND A WEAK ACID, SAID AQUEOUS SOLUTION HAVING A PH VALUE HIGHER THAN 11.0 BUT NO HIGHER THAN 12.8 AFTER DILUTION 100 TIMES. 